Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Distance”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,153 records · Page 64Linked to original sources
PubMed1990

Proximal vergence and perceived distance.

Proximal vergence was measured haploscopically in response to a change in physical distance of a large screen of blurred horizontal lines. These responses were compared to proximal vergence measurements made using a clinical method. Perceived distance of the horizontal stripes was estimated according to the perceived size of a projected afterimage. For 18 normal observers the change in vergence measured haploscopically (in prism diopters per meter angle change in test distance) averaged 2.59 (SD = 1.44) binocularly and 2.11 (SD = 1.22) monocularly. Clinical measures averaged 2.88 (SD = 1.57) binocularly and 2.10 (SD = 1.27) monocularly. Haploscopic and clinical measures of proximal vergence correlated only when the clinical technique was modified by viewing through pinholes. Taking estimated perceived distance into consideration only partially reduced the differences between proximal vergence measured haploscopically and clinically as well as binocularly and monocularly. Both haploscopic and clinical measures of proximal vergence were sizeable, indicating that this vergence component can contribute significantly to the normal vergence response.

Accommodation, Ocular↗
PubMed1992

Variation of congenital nystagmus with viewing distance.

Involuntary oscillations of the eyes in persons with congenital nystagmus often dampen in intensity (amplitude x frequency) with near viewing. This study examined how changes in viewing distance affect the duration and position variability of foveation periods (intervals of low eye velocity when the target's image is at or near the fovea), as these parameters generally correlate better with acuity than nystagmus intensity. To do so, the horizontal positions of both eyes were recorded by infrared limbal tracking in 4 subjects with congenital nystagmus and 4 normals during monocular and binocular fixation at 200, 40, and 20 cm. At nearer distances, position variability (the standard deviation of horizontal eye position) increased in normal subjects, as well as during foveation periods in the subjects with nystagmus. Other parameters of the nystagmus varied idiosyncratically with viewing distance. In none of the subjects with nystagmus was visual acuity (measured psychometrically) better at 40 cm than at distance. The results show that characteristics of congenital nystagmus do not necessarily improve and, in some instances worsen, with near viewing.

Distance Perception↗
PubMedDate not supplied

Student perspectives on transitioning to new technologies for distance learning.

This article reports on students' perceptions of their learning experiences when an existing distance-learning master's program transitions to new technologies and new instructional strategies. Unique elements addressed in this article include (1) findings when a program with extensive experience delivering distance education changes to new technologies and (2) findings when a multidimensional format is used to evaluate program delivery. The technology changes involved migrating from a satellite-based technician-supported videoconferencing system to a land-based faculty-operated videoconferencing system and the addition of class Web materials and asynchronous computer conferencing to course delivery. The multidimensional evaluation format examined student experiences within the context of specific interactions among instructional activities, technology applications, and desired learning outcomes. The evaluation process involved (1) open-ended and structured items in course surveys and (2) an end-of-year student focus group discussion. A formative evaluation approach was used; this article reports on efforts to address the problems identified. Findings include (1) program planners should not assume that prior institutional experiences with distance education facilitate a smooth transition to use of different technologies and (2) a formative multidimensional approach to program evaluation is critical for understanding student experiences with technology-mediated distance education.

Adaptation, Psychological↗
PubMedDate not supplied

Implementation and evaluation of a medical informatics distance education program.

OBJECTIVE: Given the need for continuing education in medical informatics for mid-career professionals, the authors aimed to implement and evaluate distance learning courses in this area. DESIGN: The authors performed a needs assessment, content and technology planning, implementation, and student evaluation. MEASUREMENTS: The needs assessment and student evaluations were assessed using a combination of Likert scale and free-form questions. RESULTS: The needs assessment indicated much interest in a medical informatics distance learning program, with electronic medical records and outcome research the subject areas of most interest. The courses were implemented by means of streaming audio plus slides for lectures and threaded discussion boards for student interaction. Students were assessed by multiple-choice tests, a term paper, and a take-home final examination. In their course evaluations, student expressed strong satisfaction with the teaching modalities, course content, and system performance. Although not assessed experimentally, the performance of distance learning students was superior to that of on-campus students. CONCLUSION: Medical informatics education can be successfully implemented by means of distance learning technologies, with favorable student satisfaction and demonstrated learning. A graduate certificate program is now being implemented.

Data Collection↗
PubMed2005

Primate memory saccade amplitude after intervened motion depends on target distance.

To keep a stable internal representation of the visual world as our eyes, head, and body move around, humans and monkeys must continuously adjust neural maps of visual space using extraretinal sensory or motor cues. When such movements include translation, the amount of body displacement must be weighted differently in the updating of far versus near targets. Using a memory-saccade task, we have investigated whether nonhuman primates can benefit from this geometry when passively moved sideways. We report that monkeys made appropriate memory saccades, taking into account not only the amplitude and nature (rotation vs. translation) of the movement, but also the distance of the memorized target: i.e., the amplitude of memory saccades was larger for near versus far targets. The scaling by viewing distance, however, was less than geometrically required, such that memory saccades consistently undershot near targets. Such a less-than-ideal scaling of memory saccades is reminiscent of the viewing distance-dependent properties of the vestibuloocular reflex. We propose that a similar viewing distance-dependent vestibular signal is used as an extraretinal compensation for the visuomotor consequences of the geometry of motion parallax by scaling both memory saccades and reflexive eye movements during motion through space.

Animals↗
PubMed1982

Neural representation of target distance in auditory cortex of the echolocating bat Myotis lucifugus.

1. Single- and multiunit recordings were obtained from neurons in the auditory cortex of the echolocating bat Myotis lucifugus, while trains of stimuli designed to simulate the bat's frequency-modulated (FM) orientation pulse and its returning echo were delivered. It was found that many neurons in the cortex responded selectively to pulse-echo pairs only if the time delay separating the artificial pulse and the echo was within a certain range. This response property is called "delay-dependent facilitation." Since echolating bats are known to utilize echo-delay information for the determination of target distance, it is postulated that these neurons are involved in the process of distance perception. 2. Two types of delay-sensitive neurons were characterized on the basis of their response patterns. P-type units had short maximum response delays, narrow delay response functions, and response latencies for pulse-echo pairs that were similar to their response latencies for single loud FM pulses. E-type units had longer maximum response delays, wide delay response functions, and pulse-echo pair response latencies that were time-locked to the echo. Another important difference between these two classes was that changes in the amplitude of the artificial echo caused systematic changes in the delay response of E-type units but not of P-type units. 3. The sharpness and stability of the delay response functions of P-type units suggested that they may encode target distance by responding at discrete echo delays. In contrast, delay tuning may not be an unambiguous determinant of echo delay in E-type units. Here, the most consistent and reliable response parameter for echo delay is the time at which the responses occurred. This suggested that echo delay could be encoded by the temporal pattern of responses in E-type units in relation to the responses evoked by the outgoing orientation cry. The different range of delay of delay sensitivity of P-type and E-type units indicates that these two mechanisms could be operating at different ranges of target distance. 4. P-type and E-type responses may not be due to different populations of neurons but to different response properties of the same population under different conditions. Evidence for this proposition was obtained by showing that in some recordings, decreases in the amplitude of the artificial pulse caused a switch in response from a long best delay, E-type response to a short best delay, P-type response. This suggested that the delay sensitivity of cortical neurons could be under the bat's control based on the intensity of its pulse emissions.

Animals↗
PubMed2001

The role of vergence in the perception of distance: a fair test of Bishop Berkeley's claim.

Binocular eye movements were measured while subjects perceived the wallpaper illusion in order to test the claim made by Bishop Berkeley in 1709 that we perceive the distance of nearby objects by evaluating the vergence angles of our eyes. Four subjects looked through a nearby fronto-parallel array of vertical rods (28-35 cm away) as they binocularly fixated a point about 1 meter away. The wallpaper illusion was perceived under these conditions, i.e. the rods appeared farther away than their physical location. We found that although binocular fixation at an appropriate distance was needed to begin perceiving the wallpaper illusion (at least for naive observers), once established, the illusion was quite robust in the sense that it was not affected by changing vergence. No connection between the apparent localization of the rods and vergence was observed. We conclude that it is unlikely that vergence, itself, is responsible for the perceived distance shift in the wallpaper illusion, making it unlikely that vergence contributes to the perception of distance as Bishop Berkeley suggested. We found this to be true even when vergence angles were relatively large (more than 2 deg), the region in which the control of vergence eye movements has been shown to be both fast and effective.

Adult↗
PubMed2005

Stereoscopic correspondence for ambiguous targets is affected by elevation and fixation distance.

Binocular correspondence must be determined if disparity is to be used to provide information about three-dimensional shape. The current study investigated whether knowledge of the statistical distribution of disparities in the natural environment is employed in this process. A simple model, which produces distributions of distances similar to those found in the natural environment, was used to predict the distribution of disparities in natural images. This model predicts that crossed disparities will be more likely as (i) stimulus elevation decreases below fixation and (ii) fixation distance increases. To determine whether these factors influence binocular correspondence for human observers, ambiguous stereograms were presented to observers, as stimulus elevation and fixation distance were manipulated. Clear biases were observed in the depth perceived in these stereograms, which were more likely to be seen as closer than fixation (i) for stimuli presented below fixation and (ii) as fixation distance increased. These results suggest that binocular correspondence is determined in a manner consistent with the distributions of disparities expected in natural scenes.

Depth Perception↗
PubMed2001

Familiarity with and social distance from people who have serious mental illness.

OBJECTIVES: This study examined the effects of familiarity with and social distance from persons who have serious mental illness on stigmatizing attitudes about mental illness. METHODS: A total of 208 community college students completed three written measures about familiarity, perception of dangerousness, fear, and social distance. Path analysis with manifest-variable structural modeling techniques was used to test a version of a model in which familiarity influences the perception of dangerousness, which in turn influences fear, which influences social distance from persons with serious mental illness. RESULTS: Most of the participants reported experience with mental illness. Scores on the three written measures largely supported the path model. Correlations between the perception of dangerousness and fear as well as between fear and social distance were particularly strong. CONCLUSIONS: Approaches to social change that increase the public's familiarity with serious mental illness will decrease stigma. Further studies are warranted that focus on how contact between members of the general public and persons who have serious mental illness may be facilitated.

Adult↗
PubMed1992

Apparent size and distance in an imaging display.

The size-distance invariance hypothesis suggests that the perceived size and the perceived distance of objects in a field viewed naturally are closely related. However, this relationship breaks down when scenes are viewed through high-power optical systems. When natural scenes are viewed through an imaging display of unity magnification, there is a reduction in their apparent size. This raises the question of whether the relationship breaks down when scenes are viewed through a low-power imaging display. A single-lens reflex camera was used as an imaging display that enabled subjects to vary the size of imaged real-world scenes. Judgments of size were found to vary with depth information in scenes and between monocular and binocular viewing, consistent with a previous finding, but judgments of distance did not vary significantly across either of these conditions. The results suggest that judgments of size and judgments of distance with imaging displays are not influenced uniformly by environmental and task variables.

Adult↗
PubMed2006

The relationship between biogenetic causal explanations and social distance toward people with mental disorders: results from a population survey in Germany.

AIMS: Several studies have found an inverse relationship between people's readiness to endorse biogenetic causal explanations of mental disorder and their desire for social distance from people with mental disorders. The aim of this study is to examine why this may be the case. METHOD: In the spring of 2001, a population survey was carried out among German citizens aged 18 years and older, living in private households. A total of 5025 interviews were conducted, reflecting a response rate of 65.1%. At the beginning of the personal, fully structured interview, respondents were presented with a vignette containing a diagnostically unlabelled psychiatric case history, either depicting a case of schizophrenia or major depressive disorder. Using five-point Likert scales, causal attributions as well as perceived dangerousness, fear and the desire for social distance were assessed. RESULTS: The more respondents endorse a brain disease as a cause, the more dangerous they believe the person with schizophrenia or major depression to be. Respondents who perceive the individual in the vignette as being dangerous express a higher degree of fear and a greater preference for social distance from these individuals. As compared with brain disease, the relationships between heredity and perceived dangerousness are less pronounced for both disorders. CONCLUSIONS: Our analysis showed that endorsing biogenetic explanations decreases the likelihood of social acceptance of people with schizophrenia and major depression. Rejecting behavioural responses in the form of social distance desired from people with schizophrenia and major depression result from cognitive emotional processes in which biogenetic causal attributions are linked to lack of self-control, unpredictability and dangerousness, which, in turn, are associated with fear of these people.

Adolescent↗
PubMed2003

Determinants of the public's preference for social distance from people with schizophrenia.

OBJECTIVE: To examine the extent to which the public's desire for social distance from people with schizophrenia is influenced by beliefs about the disorder and stereotypes about those suffering from it. METHODS: In spring 2001, we carried out a representative survey of individuals of German nationality aged 18 years and over (n = 5025). Each subject was given a fully structured interview that began with the presentation of a vignette. RESULTS: Both labelling and beliefs about the disorder's causes and prognosis, as well as the perception that those suffering from it are unpredictable and dangerous, had an impact on the public's desire for social distance. However, the latter proved to be more important. As expected, respondents who identified the disorder depicted in the vignette as mental illness, those who blamed the individual for its development, and those who anticipated a poor prognosis expressed a stronger desire for social distance. Endorsing biological factors as a cause was also associated with increased social distance. CONCLUSIONS: Our findings have important implications for interventions aimed at reducing stigma and discrimination related to schizophrenia. Targeting the stereotype of unpredictability and dangerousness appears to be particularly important.

Adolescent↗
PubMed2002

Distance learning in a school nurse credential program.

Distance learning, which encompasses many methodologies, is becoming a more readily available educational alternative. Because there are a limited number of school nurse credential programs and the demand for school nurses is increasing, distance learning may be a viable method of instruction. This article describes the authors' experiences organizing and presenting distance learning courses to five remote sites for students in a university school nurse credential program. After numerous inquiries, potential students from several areas were surveyed, and arrangements were made with universities in those areas to receive two-way audio and video transmissions of two seminar courses; later, two clinically oriented courses in the school nurse program. Students were able to complete their program requirements by taking equivalent course work at their local universities. Perceptions of students and the instructor, course evaluation, and practical suggestions are shared. Guidelines for potential students about selecting quality distance education programs are also noted.

California↗
PubMed2005

Keeping the ball in the air: contact in long-distance friendships.

As people continue to be more mobile, maintenance behaviors for long-distance friendships will continue to be a part of the relocation experience. In this qualitative study, 25 women age 45 and over, who had relocated a number of times, were asked to talk about how their friendships had transitioned to being long-distance relationships and what current maintenance behaviors entailed. Communication was a major theme involving electronic mail (e-mail), Christmas cards, telephone calls, and visits. Results from the current study suggest that maintaining the perception of the existence of a well-connected social support system could be accomplished with a single, annual contact. Further, the long-distance friendship biographies explored in this study provided characteristics of friendship maintenance behavior that could be grouped into three main categories forming a proposed typology of long-distance friendship maintenance.

Aged↗
PubMed1989

Distance from mother and father among alcoholics.

The relationship of parental closeness to current behavior and related psychopathological indices is studied among alcoholics. Seventy alcoholics from an inpatient treatment unit and thirty medical inpatients were given a battery of alcohol related measures. These measures included a scale assessing the psychological distance from mother and father, a social closeness measure, an index of anger, a locus of control measure, along with basic alcohol-related information. In addition, the alcoholic sample was given psychometric measures of depression and cognition. Results show that perceived distance from parents is greater among alcoholics than medical patients. Comparison analyses of mother and father distance scores on the study variables of alcohol-related and psychometric measures yielded only a few differences. Correlational analyses showed, however, that distance from mother and father is related to parental alcohol abuse and parents not being at home but not to current behavior (except anger).

Adult↗
PubMed2002

Reading at a distance: implications for the design of text in children's big books.

BACKGROUND: Visual acuity, typically measured by the ability to name letters at a distance, is poorer when letters are small and closely spaced. It has been suggested that reading can be affected by letter size and spacing. AIM: To determine the effect of text size and spacing on the ability to read at a distance, with a view to helping with the design of text in children's 'Big Books'. SAMPLE: The visual acuity of 200 children aged between 6 and 12 was measured. A subset of 66 children was given further reading tests. METHOD: From a viewing distance of 3m children were required (1) to identify words and (2) to read passages of text rapidly. A repeated measures design was used to compare the effects of different size and spacing of text on performance of the two tasks. RESULTS: Performance improved when the spacing of words and size of letters was greater than is typical in 'Big Books'. For a given letter density, increasing the spacing improved performance more than increasing the letter size. CONCLUSION: The text in children's books could be made easier to read by expanding the spacing between words and also by increasing the size of the print. The maximum viewing distance should be reduced from 15ft (4.6m) to 10ft (3.0m).

Child↗
PubMed2004

[Distance learning in the nursing area: report of an experience].

This study aims at reporting an experience of offering a course in the master program of the Universidad Nacional de Rosário. The purpose is to offer elements for a reflection on a conception of long-distance education, as an adequate and efficient modality of education, aiming at enabling a teaching with quality to a determined clientele. The course was developed in three moments: video-conference, long-distance didactic activities and a seminar. The tutoring was shared by establishing the challenge of having a dialogic relation with the students. Authors believe that long-distance education is an adequate pedagogical tool to qualify nurses who have no access to traditional graduate studies. Therefore it enables the qualification of a greater number of nurses, geographically dispersed, who are unable to scape from the routine of their personal and professional lives. Facing the need to form the country's nursing workers and qualify nurses to act as teachers, long-distance learning is an effective and possible pedagogical strategy.

Education, Distance↗
PubMed1976

Determinants of personal space in young children: perception of distance cues.

Two methods of assessing personal space in young children were examined in a group of 24 boys and 24 girls, aged 3 to 6 yr. When sex of peer figures and affect attributed to them were varied, 3-yr.-olds made distance-cue judgements based on affect but failed to use affect cues in structuring personal space. However, 4- to 6-yr.-olds readily perceived and used distance to communicate the affective quality of peer relations. On both measures, perception of distance cues increased with age. Only girls also used sex of figures as a social cue in depicting appropriate distances.

Affect↗